Inflatable form for concrete building shell

ABSTRACT

An inflatable form for a concrete building shell comprising a frame including a plurality of support members defining the periphery of a concrete shell segment, a retainer affixed to one support member and affording a continuous channel facing outwardly of the support member, and a wood rail wrapped in one edge of an outer fabric layer for the inflatable form. The rail is dimensioned to fit easily into the channel in flat relation thereto, but is large enough to lock firmly into the channel upon inflation of the form. In a preferred embodiment, there is an auxiliary rail positioned within the channel, below the main rail and outside the fabric, held in place by a plurality of small wedges.

United States Patent 1 3,719,341 I Harrington March 6, 1973 1 INFLATABLEFORM FOR CONCRETE FOREIGN PATENTS OR APPLICATIONS BUILDING SHELL 914,430l/l963 Great Britain ..52/222 [75] Inventor: Horrall Harrington,Pittsburgh, Pa. 73 Assignee; Ivan Himmd, Chicago, n a part PrimaryExaminer-J. Spencer Overholser interest Assistant Examiner-John S. BrownAttorney- Kinzer and Dorn [22] FIled: July 26, 1971 [21 Appl. No.:165,478 ABS RACT An inflatable form for a concrete building shell com-52 us. Cl. ..249/65, 5212, 52/222 prising a frame including a pluralityof Support [5l] Int. Cl. ..B28b 7/32 bets fining the periphery of aconcrete shell seg- [58] Field of Search ..425/5l, 59, 62, 63, 389, 817;men, a retainer affixed to one pp member and 264/32, 33, 34, 314;249/11, 20, 65,10,117; 52/2, 63, 222; 135/3 R, l R, 15 CF affording acontinuous channel facing outwardly of the support member, and a woodrail wrapped in one edge of an outer fabric layer for the inflatableform.

[ 56] References Cited The rail is dimensioned to fit easily into thechannel in flat relation thereto, but is large enough to lock firmlyUNITED STATES PATENTS into the channel upon inflation of the form. In a1 178 338 4/1916 Niersee 135/3 R preferred embodiment, there is anauxiliary rail posi- 3:643:9lO 2/1972 Heifetz ..249/65 (med within thechannel below the main and outside the fabric, held in place by aplurality of small wedges.

10 Claims, 5 Drawing Figures 67 A l l 7) 6 6 9 f l 75 25 PATENTED 619753.7 1 9 341 SHEET 10F 2 j I I [\fi V k\ H 62 65 65 62 INVENTOR HO RRALLHARRINGTON v ATTORNEYS PATENTED 51975 SHEET 2 [IF 2 INVENTOR HORRALLHARRINGTON .12 2M KW" TT I ORNEYS v INFLATABLE FORM FOR CONCRETEBUILDING SHELL CROSS REFERENCES TO CO-PENDING APPLICATIONS Thisinvention is an improvement upon the inflatable form structuresdisclosed in the co-pending application of Horrall Harrington, Ser. No.760,297 and now US. Pat. No. 3,619,432, filed Sept. 17, 1968, entitledMethod and Apparatus for Construction of Concrete Shells.

BACKGROUND OF THE INVENTION Concrete shells have been in use for manyyears. A substantial body of technical literature on stress analysis anddesign data is available on structures of this kind and many concreteshell buildings have been erected, primarily in Europe and LatinAmerica. Comprehensive design data for concrete shells is available fromthe Portland Cement Association.

One technique that has been successfully employed in the erection ofconcreteshell structures utilizes a comprehensive fabric form, much likean enormous tent, for the complete shell. The form is inflated to afforda continuous cover for the building structure. The concrete is appliedto the surface of the fabric form while the form is inflated. Theconcrete may be applied to the exterior of the fabric form;alternatively, the concrete is applied to the internal surface of theform, as disclosed in United States Patent No. 3,118,010 to HorrallHarrington, issued January 14, 1964.

Another and improved technique for erecting concrete shell buildingsutilizes a form assembly comprising a rigid structural frame with atwo-layer flexible inflatable form mounted on the frame. The frame has aconfiguration generally conforming to one segment of the desiredconcrete shell. The form assembly is aligned with a part of the buildingfoundation and the form is inflated. Metal reinforcements are thenpositioned on the external surface of the form. Concrete is depositedover the form surface and permitted to set, after which the form isdeflated and the form assembly is moved to a new position adjacent thecompleted seg ment of the concrete shell to permit construction of thenext shell segment. This particular technique, described in Harringtonapplication Ser. No. 760,297, affords substantial advantages withrespect to construction of different building shapes and configurations,producing practical, inexpensive, multisegment shell structures.

In the use of inflatable forms constructed of woven or other likeflexible material referred to generically herein as fabric, substantialdifficulty may be encountered in securing the edges of the fabric to aframe or other support structure. This is particularly true with respectto the two-layer inflatable form employed in the preferred buildingmethod described above. If the edges of the form are fastened down byretaining strips that use nails, bolts, screws, or other fasteners thatproject through the fabric, there is a tendency for the fabric of theform to tear, particularly on repeated use of the form in constructingmulti-segment shells. Moreover, conventional fastening means make itdifficult to remove the fabric portion of the form from a supportingstructure for re-use in a different construction job, since the edgeportions of the fabric are almost inevitably damaged during use or onremoval.

SUMMARY OF THE INVENTION It is a principal object of the presentinvention, therefore, to provide a new and improved means for mounting atwo-layer inflatable flexible form on a supporting structure for use inthe erection of a concrete building shell.

A further object of the invention is to provide a new and improved meansfor mounting a two-layer fabric form on a support structure that permitsconvenient removal of the fabric part of the form from the supportstructure for repair or replacement purposes or for reuse on a differentsupport structure.

An additional object of the invention is to provide a simple andinexpensive mounting means for mounting the edge of the fabric of aninflatable concrete building shell form on a support member withoutrequiring the use of screws, bolts, nails or other elements that projectthrough the fabric of the form.

Accordingly, the invention relates to a form assembly for constructing aconcrete shell for a building of the kind comprising a wall structuredefining the perimeter of a building space and a concrete shell coveringthat space. The form assembly of the invention comprises a rigidstructural frame, conforming to the configuration required for onesegment of the concrete shell and having a plurality of form-supportingmembers extending around the perimeter of the frame. An inflatable formis mounted on the frame and affords a substantially air-tight chamberspanning the space between the form-supporting members, the inflatableform including an outer layer formed of a strong, relatively inelasticfabric. A retainer member is affixed to one of the support members andaffords a substantially continuous channel of given height and widthfacing outwardly of the space spanned by the fabric outer layer of theinflatable form. A rail member is wrapped in the edge portion of thefabric outer layer corresponding to the aforesaid one support member;the rail member has a height smaller than the height of the retainerchannel but has an' effective diagonal thickness substantially greaterthan the effective internal height of that channel, permitting readyinsertion of the rail member and the edge portion of the fabric outerlayer into the retainer channel when the form is deflated for releasablemounting of said outer fabric layer on said frame. The rail memberrotates within the retainer channel into locking engagement therewithupon inflation of the form.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, partlyin section, of a portion of a building incorporating a partiallycompleted multi-segment concrete shell erected by means of an inflatableform in accordance with the method described in Harrington applicationSer. No. 760,297;

FIG. 2 is a sectional elevation view taken approximately along line 22in FIG. 1;

FIG. 3 is a detail sectional view of a part of the form assembly, takenalong line 3-3 in FIG. 2, with the form deflated, illustrating oneembodiment of the present invention;

FIG. 4 is a sectional view like FIG. 3 but with the form inflated; and

FIG. 5 is a sectional view, like FIG. 4, of another embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the erection of a concreteshell building using an inflatable form, it is first desirable to erecta wall structure defining the building space to be covered by theconcrete shell. The concrete shall can start from ground level, in whichcase the wall structure may comprise simple footings. In manyapplications, however, it is desirable to use continuous vertical wallsor a plurality of columns around the periphery of the building,affording a wall structure that extends above ground level. The termwall structure, as used herein, is intended to encompass a continuousfooting, a continuous wall above grade level, a plurality of verticalcolumns, or any combination thereof.

For a generally rectangular building having vertical side and end walls,the basic foundation structure may be as illustrated in FIG. 1,comprising two side walls 20 and 21. Walls 20 and 21 may be of anyconventional structural material, including concrete, steel, or wood, solong as they have adequate strength for supporting the concrete shellthat is to cover the building. Walls 20 and 21 may be supported uponsuitable footings below the ground surface, as illustrated in FIG. 2. Afloor 22 extending between walls 20 and 21 may be formed before theshell is constructed, as a part of the foundation structure. On theother hand, floor 22 may be constructed after the shell has beencompleted. In the building shown in the process of erection in FIG. 1,no end walls between the side walls 20 and 21 have as yet been erected;the construction of the end walls for the building has been deferreduntil after erection of the shell.

In the erection of the concrete shell, a form assembly 23 is employed.Form assembly 23 comprises a rigid structural frame 24 including fourperipheral form support members 25, 26, 27, and 28. For the particularbuilding shown under erection in FIG. 1, the support members 25-28 offrame 24 are of linear configuration, conforming to the requiredconfiguration for the front and rear edges of each segment of theparticular concrete shell that is to constitute the building roof. Forother shell shapes the form support members, particularly members 25 and26 extending between walls 20 and 21, may be of arcuate or othernon-linear configuration. Two concrete shell segments 29 and 30 havealready been completed, in the building illustrated in FIG. 1. Thesupport members 25-28 may be formed of steel, laminated wood, or anyother suitable structural material or combination of materials affordingsufficient strength to hold theshape of a fabric form; steel ispreferred for a part of the support members as described more fullyhereinafter.

Form assembly 23 further comprises an inflatable form mounted on andspanning the space between the support members 25-28 of frame 24. Asshown in FIGS. 2, 3 and 4, the inflatable form comprises an outer fabriclayer 31 and a lower deck 32 across the support members. The fabriclayer 31 and deck 32 afford a substantially air-tight chamber 33 betweenthem. It is not essential that the chamber 33 be absolutely air-tight.In fact, pressure venting may be desirable to facilitate maintenance ofa constant pressure within chamber 33 during use of the form assembly23. Furthermore, small tears or other holes in either fabric layer 31 ordeck 32 can be tolerated and can be compensated by providing an adequatesupply of air.

In the building under construction, as illustrated in FIG. 1, the twoside walls 20 and 21 are parallel to each other. The frame 24 of formassembly 23 spans the space between the two building walls 20 and 21 andthe inflatable form 31,32 covers the entire space between the supportmembers 25-28. Thus, frame assembly 23 spans a complete segment of thebuilding between the two walls 20 and 21 and extends into closeconjunction with the walls.

The frame 24 of form assembly 23 is supported upon a series of jacks 35,as generally indicated in FIG. 2. Jacks 35 may be of conventionalconstruction. Preferably, frame 24 is mounted on wheels (not shown)positioned to support form assembly 23 when jacks 35 are not in use, tofacilitate movement of the form assembly to a new location.

Form assembly 23 also includes means for introducing air under pressureinto the chamber 33 formed by fabric layer 31 and deck 32. This airpressure means may comprise a simple hose or other conduit 51 mounted indeck 32 and connected from chamber 33 to a blower 53 mounted in frame 24below deck 32. Only a relatively small blower is required; commerciallyavailable centrifugal blowers are adequate for use as blower 53. In mostapplications, a five to ten horsepower centrifugal blower is adequate tomaintain the appropriate pressure for inflation of the form. One or moreindividual relief valves or other pressure control valves may beincorporated in either fabric layer 31 or deck 32 to provide a means formaintaining a uniform pressure within chamber 33 when the form isinflated.

In considering the erection of a concrete shell segment, a startingpoint may be taken from the position of form assembly 23 shown inFIG. 1. From the illustrated position, the form assembly is moved intoalignment with the already completed shell segment 30. Thismovement isaccomplished with the frame 24 of the form assembly lowered, by means ofjacks 35, so that there is a clearance of at least one or two inchesbelow the projecting edge 55 of shell segment 30. Moreover, the movementof the form assembly into position is preferably accomplished with theform 31,32 deflated. The form has been shown inflated in FIG. 1, merelyto correlate its shape with the completed shell segments 29 and 30; whendeflated, fabric layer 31 lies flat across deck 32 (see FIG. 3).

When form assembly 23 is aligned with the previously completed shellsegment 30 and is also aligned with the portion of the wall structure(walls 20 and 21) that is to be spanned by the next shell segment, theform assembly is blocked in position by any appropriate means. Blower 53is then actuated to force air under pressure into the chamber 33intermediate fabric layer 31 and deck 32, inflating the fabric form tothe condition illustrated in FIGS. 1, 2 and 4.

After the form is inflated, metal reinforcing members (not shown) arepositioned on the external surface of fabric layer 31. Once the metalreinforcing members are in place on and supported by the inflated fabricform, a layer of concrete is deposited on the external surface of thefabric form, covering the reinforcing members. This concrete layerusually extends beyond the edge of form 23 as indicated by the dash line56 in FIG. 4. Along support members 27 and 28, the outer extension ofthe concrete tops walls 20 and 21, so that the concrete rests on and andbonds to the wall structure of the building. Wet mix pneumaticapplication is most effective for depositing the concrete although, withproper care to avoid damage to fabric 31, conventional crane and bucketapplication can be used. Even on steeply sloped surfaces, pneumaticplacement is made possible by application in layers not exceeding oneinch in thickness. For more nearly horizontal surfaces, thicker layersmay be employed.

Once the concrete has set, the shell segment is complete and it is timeto move the form assembly into position for the next shell segment. Theform is deflated to release the upper fabric layer 31 from the concrete.This can be most effectively accomplished by changing the connection toblower 53 and using the blower to exhaust chamber 33, affording arelatively small vacuum within the chamber to assist in separation ofthe fabric from the concrete of the shell. The jacks 35 are then used tolower form assembly 23 enough to assure clearance from the shell segmentthat has just been formed, and the form assembly is rolled out fromunder the completed shell segment. It is then ready to be aligned withthe leading edge of the completed shell segment and the steps set forthabove are repeated to form the next shell segment. I

FIGS. 3 and 4 illustrate the mounting assembly of the present invention,utilized to secure the edge portion of fabric layer 31 to support member25 in frame 24. As shown in FIGS. 3 and 4, support member 25 comprisesan elongated steel plate 61 mounted on a major structural element 62 ofthe form assembly 24. Member 62 may comprise a conventional wood beam. Aplurality of bolts 63 extending downwardly through plate 61, adjacentbeam 62, and througha mounting plate 64 on the bottom of the beam, beingthreaded into the nuts 65. Plate 61 is similarlysecured to otherstructural elements of the main frame 24 of form assembly 23; othersuitable mounting arrangements may be employed if desired. Beam 62 isalso one of the supports for the deck 32 that constitutes the bottomlayer of the inflatable form as described above in connection with FIG.2.

A retainer member 66 is afiixed to the steel plate 61 of support member25. As shown in FIGS. 3 and 4, retainer member 66 preferably comprises asteel angle member welded to plate 61 along one edge 67. Retainer member66 extends for the full length of support member 25 and affords asubstantially continuous channel of given height and width facingoutwardly of the space spanned by the outer fabric layer 31 of theinflatable form. A series of brace members 68 may be mounted upon plate61 in engagement with the back of the angle retainer member 66 to bracethe retainer member against the forces applied thereto when the form isinflated.

A rail member 69 is wrapped in the edge portion 71 of the fabric outerlayer 31 that extends along support member 25. Rail member 69 ispreferably an inexpensive wood rail of rectangular cross-sectionalconfiguration. The rail member has a height smaller than the height ofthe channel afforded by angle retainer member 66, but the diagonaldimension of rail 69 is greater than the effective internal height ofthe channel. The wrapping of rail 69 in the edge portion 71 of fabriclayer 31 is not elaborate; the fabric is simply passed around the railone time and the free end 72 of the fabric is laid back across the topof retainer member 66. As is readily apparent from FIG. 3, rail member69 and the fabric edge portion 71 fit loosely into the channel 70,permitting ready insertion thereof into the channel when the form isdeflated, as shown in FIG. 3. This construction affords a convenientreleasable mounting of the outer fabric layer 31 on frame 24 of formassembly 23. It also permits convenient removal of the fabric from theframe of the form if there is any damage to the fabric requiringreplacement thereof or if use of the form assembly has been completedand it is desired to employ the fabric layer 31 in another formassembly.

After fabric layer 31 is mounted on support member 25, as shown in FIG.3, it may be desirable to add an auxiliary form, extending beyond theedge of fabric layer 31, to provide for formation of a rim or edgeportion on the concrete shell. As shown in FIG. 4, this auxiliary formmay comprise a vertically extending form member 73 and a horizontallyextending form member 74, both mounted upon a support block or beam 75that extends parallel to support member 25. The auxiliary form structureis supported upon the beams 62 of frame 24.

When air is introduced under pressure into the chamber 33 between theouter fabric layer 31 and the deck 32, the fabric layer 31 expands tothe desired configuration for a segment of the concrete shell, asgenerally illustrated in FIGS. 1 and 2. The fabric is lifted clear ofdeck 33 and pulls upwardly and inwardly of the form assembly frame asindicated by arrow A in FIG. 4. A substantial tension force is exertedon the fabric, in the direction of arrow A, since form 31 must bemaintained taut enough to support a substantial weight of concrete andsteel reinforcement without appreciable deformation and is preferablymaintained under sufficient pressure to support workmen and a limitedamount of equipment on the fabric during placement of the reinforcementand pouring of the concrete.

The pull exerted upon the fabric layer 31 rotates rail 69 within channel70. The rotation of rail 69 locks the comers of the rail into engagementwith the internal walls of channel 70 and maintains a firm mount forfabric 31 when the form is inflated. Because the fabric edge portion 71encompasses rail 69, and since there are no nails, screws, or otherfasteners extending through the fabric into rail 69 or any other portionof the mounting structure, the inflation of the form does not damage thefabric outer layer. In fact, the form can be inflated and deflatednumerous times, in the erection of a building, with little or no damageto the edge portion of fabric layer 31, using the mounting assemblyillustrated in FIGS. 3 and 4. Nevertheless, when use of the formassembly 23 is completed, or if fabric layer 31 has been damaged in anyway during use, the fabric layer can be rapidly removed from the formassembly simply by deflating the form and pulling rail 69 out of channel70. Where an edge form, such as the auxiliary form 73-75, is used, itmay be necessary to remove the auxiliary form to permit removal offabric 31, but this would also be necessary with virtually any othermounting arrangement for the fabric.

FIG. 5 illustrates another embodiment of the mounting assembly of theinvention in a view similar to FIG. 4, with the form inflated. In theconstruction illustrated in FIG. 5, the edge support member 125 of aform assembly frame 124 comprises a tubular steel frame member. On thetop of support member 125, a steel angle retainer member 66 is welded tothe support member. Retainer member 66 extends longitudinally of supportmember 125 to form a substantially continuous channel 70 of given heightand width facing outwardly of the space spanned by the fabric outerlayer 32 of the inflatable form.

In the mounting assembly of FIG. 5, two rail members 169 and 171 areused to mount the edge portion 71 of fabric 32 in channel 70. The mainrail member 169 is wrapped in the edge portion 71 of fabric 32 in thesame manner as rail 69 in FIGS. 3 and 4, with the free end 72 of thefabric extending back into the inflation chamber 133 of the formassembly. Rail member 169 is substantially thinner than the rail memberof the previously described embodiment; typically, an ordinary woodfurring strip can be used as rail member 169. The auxiliary rail member171 may also be an ordinary wood furring strip. Auxiliary rail member171 is inserted into channel 170 below the principal rail member 169 andoutside of the edge portion 71 of fabric 32. Thus, the auxiliary railmaterially reduces the effective internal height of channel 70.

The mounting assembly of FIG. 5 further comprises a plurality of thesmall wood wedges 172 that are inserted into channel 70, from the openend of the channel, between support member 125 and rail 171. Wedges 172are not forced into channel 70 under any great pressure; they may betapped into place with an ordinary carpenters hammer. Wedges 172 servesimply to clamp rails 169 and 171 and the edge portion 172 of the fabricinto channel 70 prior to inflation of the form. After fabric 32 has beenpositioned on the form, an auxiliary edge retaining form, comprisingform members 73, 74, 75A and 758, may be mounted on support member 125to make the form assembly ready for operation. Suitable brackets 76 maybe provided to support the outer members of the auxiliary edge form.

In the construction illustrated in FIG. 5, there is no continuous deckfor the inflatable portion. Instead, a second fabric layer 231 isprovided and constitutes the bottom of the inflatable form. To mountfabric layer 231 on the frame 124 of the form assembly, and specificallyon support member 125, a mounting arrangement like that for the upperfabric layer 32 is used. The mounting for the lower fabric layer 231includes an angle retainer 266 welded to support member 125 and forminga continuous channel 270 that faces outwardly of the inflatable chamber133. A principal rail 269 wrapped in the edge portion 271 of fabriclayer 231, and an auxiliary rail 277, together with a plurality of smallwedges 272, serve to mount the edge portion of fabric 231 in channel 270in the same manner as described for fabric layer 32 and channel 70.

The operational characteristics for the mounting assembly illustrated inFIG. 5 afford all of the advantages achieved by the construction ofFIGS. 3 and 4. In assembling the inflatable form, the upper fabric layer32 is spread loosely over the frame 124. The lower fabric layer 231 maybe supported on any desired temporary support; a series of ropesspanning the bottom portion of frame 124 will serve. The edge of fabric32 is wrapped in rail 169, the wrapped rail 169 and the auxiliary rail171 are inserted into channel 70, and the rails are wedged in place bywedges 172 as shown in FIG. 5. The fabric is not in tension at this timeand the mounting arrangement can be accomplished quickly by a limitednumber of workmen. The same technique is followed for fabric layer 231,with the edge portion being wrapped around layer 231 and the rails 269and 271 then being inserted into channel 270 and wedged in place bywedges 272.

The form can then be inflated. The tension on the fabric layers 32 and231, indicated by the arrows A and B, rotates the rails within thechannels afforded by retainer members 66 and 266 and firmly locks theedges of the fabric layers in place, as shown in FIG. 5, without damageto the fabric. Thus, the mounting assembly performs its primary functionof affording a secure and continuous anchorage for the fabric layers ofthe form despite the high tension forces created in the fabric by theinflation air pressure. In addition, the fabric mounts each afford atight seal against air leakage, in contrast with other mountingarrangements requiring piercing of the fabric. The illustrated mountingarrangements also afford secure maintenance of the fabric edge positionduring installation and during random movements of the fabric that mayoccur as air pressure builds up in the inflatable form.

The tension in the fabric layers, indicated by arrows A and B in FIG. 5,pulls the principal rails 169 and 269 against the inner surfaces oftheir respective retainer members 66 and 266. As a consequence, the edgeportion of each of the fabric layers 32 and 231 is effectivelymaintained in a continuous vise in which the clamping force of the viseincreases as a direct function of fabric tension. This action is aidedby the high friction restraint at each bend of the fabric around thecorners of the principal rails. Wedges 172 and 272 serve only for thetemporary purpose of maintaining fabric position during air pressurechanges for inflation and deflation.

In both of the illustrated embodiments of the invention, the clampingmeans for the fabric does not subject the fabric to any cutting or othersevere mechanical attrition, facilitating re-use of the fabric after theform assembly is dismantled. The use of wood for the rails 69, 169 and269, and for the auxiliary rails 171 and 277, facilitates the preventionof damage to the edge portions of the fabric. The use of wood rails forthis purpose is also advantageous from an economical standpoint.Furthermore, the wood for the rails is generally available from anylumber yard; ordinary furring strips perform this function quiteadequately.

I claim 1. A form assembly for constructing a concrete shell for abuilding comprising a wall structure defining the perimeter of abuilding space and a concrete shell covering that space, said formassembly comprising:

a rigid structural frame, conforming to the configuration required forone segment of said concrete shell and having a plurality ofform-supporting members extending around the perimeter of said frame;

an inflatable form, mounted on said frame and affording a substantiallyair-tight chamber spanning the space between said form-supportingmembers,

said inflatable form including an outer layer formed of a strong,relatively inelastic fabric;

a retainer member, affixed to one of said support members and affordinga substantially continuous channel of given height and width facingoutwardly of the space spanned by the fabric outer layer of saidinflatable form;

and a rail member, wrapped in the edge portion of said fabric outerlayer corresponding to said one support member, said rail member havinga height smaller than the height of said channel but having an effectivediagonal thickness substantially greater than the effective internalheight of said channel, permitting ready insertion of said rail memberand the edge portion of said fabric outer layer into said channel whenthe form is deflated for releasable mounting of said outer fabric layeron said frame, said rail member rotating within said channel intolocking engagement therewith upon inflation of said form.

2. An inflatable form according to claim 1, in which said support memberand said retainer member are both formed of metal and are joinedtogether to form a continuous channel integral with the support member.

3. An inflatable form according to claim 2 in which said retainer memberis a steel angle edge-welded to a steel support member.

4. An inflatable form according to claim 3 and further comprising aplurality of brace members mounted on said support member and eachengaging the back of said angle retainer member to brace said retainermember against the forces applied thereto upon inflation of said form.

5. An inflatable form according to claim 1 in which said rail member isa single wood rail of rectangular cross-sectional configuration.

6. An inflatable form according to claim 1 in which said rail member isa wood rail and further comprising an auxiliary wood rail memberinserted into said channel below the principal rail member andexternally of said fabric.

7. An inflatable form according to claim 6 in which both said railmembers are of rectangular cross-sectional configuration.

8. An inflatable form according to claim 7 and further comprising aplurality of wedges inserted into the bottom open end of said channel,beneath said auxiliary rail member, to clamp the edge of said outerfabric layer into said channel prior to inflation.

9. An inflatable form according to claim 1 in which said inflatable formfurther comprises a second fabric layer, located below said outer layerand mounted on said frame by means of a second retainer member and asecond rail member corresponding in construction to the retainer memberand rail member for said outer fabric layer.

10. An inflatable form according to claim 1 in which said inflatableform comprises a relatively rigid deck, mounted on said frame, saidchamber being formed between said outer fabric layer and said deck.

1. A form assembly for constructing a concrete shell for a buildingcomprising a wall structure defining the perimeter of a building spaceand a concrete shell covering that space, said form assembly comprising:a rigid structural frame, conforming to the configuration required forone segment of said concrete shell and having a plurality ofform-supporting members extending around the perimeter of said frame; aninflatable form, mounted On said frame and affording a substantiallyair-tight chamber spanning the space between said form-supportingmembers, said inflatable form including an outer layer formed of astrong, relatively inelastic fabric; a retainer member, affixed to oneof said support members and affording a substantially continuous channelof given height and width facing outwardly of the space spanned by thefabric outer layer of said inflatable form; and a rail member, wrappedin the edge portion of said fabric outer layer corresponding to said onesupport member, said rail member having a height smaller than the heightof said channel but having an effective diagonal thickness substantiallygreater than the effective internal height of said channel, permittingready insertion of said rail member and the edge portion of said fabricouter layer into said channel when the form is deflated for releasablemounting of said outer fabric layer on said frame, said rail memberrotating within said channel into locking engagement therewith uponinflation of said form.
 1. A form assembly for constructing a concreteshell for a building comprising a wall structure defining the perimeterof a building space and a concrete shell covering that space, said formassembly comprising: a rigid structural frame, conforming to theconfiguration required for one segment of said concrete shell and havinga plurality of form-supporting members extending around the perimeter ofsaid frame; an inflatable form, mounted On said frame and affording asubstantially air-tight chamber spanning the space between saidform-supporting members, said inflatable form including an outer layerformed of a strong, relatively inelastic fabric; a retainer member,affixed to one of said support members and affording a substantiallycontinuous channel of given height and width facing outwardly of thespace spanned by the fabric outer layer of said inflatable form; and arail member, wrapped in the edge portion of said fabric outer layercorresponding to said one support member, said rail member having aheight smaller than the height of said channel but having an effectivediagonal thickness substantially greater than the effective internalheight of said channel, permitting ready insertion of said rail memberand the edge portion of said fabric outer layer into said channel whenthe form is deflated for releasable mounting of said outer fabric layeron said frame, said rail member rotating within said channel intolocking engagement therewith upon inflation of said form.
 2. Aninflatable form according to claim 1, in which said support member andsaid retainer member are both formed of metal and are joined together toform a continuous channel integral with the support member.
 3. Aninflatable form according to claim 2 in which said retainer member is asteel angle edge-welded to a steel support member.
 4. An inflatable formaccording to claim 3 and further comprising a plurality of brace membersmounted on said support member and each engaging the back of said angleretainer member to brace said retainer member against the forces appliedthereto upon inflation of said form.
 5. An inflatable form according toclaim 1 in which said rail member is a single wood rail of rectangularcross-sectional configuration.
 6. An inflatable form according to claim1 in which said rail member is a wood rail and further comprising anauxiliary wood rail member inserted into said channel below theprincipal rail member and externally of said fabric.
 7. An inflatableform according to claim 6 in which both said rail members are ofrectangular cross-sectional configuration.
 8. An inflatable formaccording to claim 7 and further comprising a plurality of wedgesinserted into the bottom open end of said channel, beneath saidauxiliary rail member, to clamp the edge of said outer fabric layer intosaid channel prior to inflation.
 9. An inflatable form according toclaim 1 in which said inflatable form further comprises a second fabriclayer, located below said outer layer and mounted on said frame by meansof a second retainer member and a second rail member corresponding inconstruction to the retainer member and rail member for said outerfabric layer.